Single sheet master for diffusion transfer

ABSTRACT

AN OFFSET MASTER ADAPTED TO BE IMAGED TO PROVIDE AN OLEPHILIC INK RECEPTIVE IMAGE BY DIFFUSION TRANSFER FROM AN EXPOSED SILVER HALIDE IN WHICH THE MASTER COMPRISES A BASE SHEET HAVING A WATER INSOLUBLE, WATER RECEPTIVE, HYDROPHILIC LITHOGRAPHIC SURFACE WITH A NUCLEATING AGENT ON THE SURFACE AND A WATER SOLUBLE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM, THORIUM AND TITANIUM, AND WITH A SILVER HALIDE NEGATIVE STRATUM FORMING AN INTEGRAL PART OF THE MASTER OVERLYING THE LITHOGRAPHIC SURFACE. A CADMIUM SALT AND A SENSITIZING DYESTUFF MAY BE INCLUDED AS A PART OF THE TREATING MATERIALS OVERLYING THE LITHOGRAPHIC SURFACE BUT UNDERLYING THE SILVER HALIDE NEGATIVE STRATUM OF THE COMPLETED MASTER.

Jan. 5, 1971 M. K. ORMSBEE 3,552,970

SINGLE SHEET MASTER FOR DIFFUSION TRANSFER Filed Nov. 17, 1966 If]! III/l III/IIIIII/II/I I I N VE N TOR Wary ZOrmsbec United States Patent Oifice 3,552,970 Patented Jan. 5, 1971 U.S. CI. 9676 7 Claims ABSTRACT OF THE DISCLOSURE An offset master adapted to be imaged to provide an oleophilic ink receptive image by diffusion transfer from an exposed silver halide in which the master comprises a base sheet having a water insoluble, water receptive, hydrophilic lithographic surface with a nucleating agent on the surface and a water soluble salt of a metal selected from the group consisting of zirconium, thorium and titanium, and with a silver halide negative stratum forming an integral part of the master overlying the lithographic surface. A cadmium salt and a sensitizing dyestuff may be included as a part of the treating materials overlying the lithographic surface but underlying the silver halide negative stratum of the completed master.

This is a continuation-in-part of my copending applications Ser. No. 526,988, filed Feb. 14, 1966, and entitled Offset Master for Imaging by Diffusion Transfer and Method of Preparation of Same, and Ser. No. 527,028, filed Feb. 14, 1966, and entitled DTR Offset Master and Method and Composition for Preparation of Same.

It is an object of this invention to produce and to provide a method for producing a new and improved offset master for imaging by diffusion transfer and it is a related object to produce a master of the type described which can be imaged in a simple and efficient manner by diffusion of silver halide from unexposed portions of a silver halide stratum and it is a related object to produce an offset master of the type described which is in the form of a coated paper master.

These and other objects and advantages of this inven tion will hereinafter appear and for purposes of illustration, but not of limitation, an embodiment of the invention is shown in the accompanying drawing in which:

FIG. 1 is a perspective view partially in section of an offset master prepared in accordance with the practice of this invention;

FIG. 2 is a sectional elevational view which schematically illustrates one method for exposure of the master;

FIG. 3 is a sectional elevational view of the imaged master after development; and

FIG. 4 is a perspective view partially in section of the imaged master.

In the aforementioned copending applications, description is made of a photolithographic master which is adapted to be imaged by diffusion transfer of silver halide, or complex formed thereof, from the unexposed portions of an exposed silver halide negative during development of the negative. Diffusion transfer is effected during development of the negative while in surface contact with the lithographic surface of the coated master wherein development is effected with an aqueous alkaline solution containing a silver halide developer and a silver halide solvent.

In accordance with the inventions described in the aforementioned copending applications, the offset or lithographic master is fabricated of a flexible base sheet having a water insoluble, water receptive, ink repellent,

hydrophilic lithographic surface, which is referred to as a silver halide receiving stratum, containing silver halide nucleating agents which operate to reduce the silver halide, or the complex formed thereof, to an ink receptive, water repellent silver image. The nucleating agent can be incorporated into the silver receptive stratum or other coatings applied to the lithographic surface by treatment with one or more solutions containing a water soluble salt of zirconium, thorium and/or titanium, and which is preferably treated, but not necessarily treated, with a water soluble salt of cadmium and/or antioxidant which may be applied together with or separate and apart from the zirconium salt.

In accordance with the teachings of the copending application Ser. No. 527,028, the treatment effected on the lithographic surface can be adapted to contain in addition to the water soluble salts of zirconium, thorium or titanium and the water soluble salts of cadmium, a sensitizing dyestuff which operates to enhance the formation of a dense image of the precipitated silver and/or an additional concentration of silver salts which can function as nucleating agents in the system described.

The concept of this continuation-in-part application resides in the further improvement in the photolithographic plate to incorporate a silver halide stratum as a part of the master thereby to make available a single sheet master which does not require the use of a separate negative for exposure and development. Thus only a one sheet process is provided in which exposure and development and treatment to form the image on the lithographic surface is made with but a single sheet.

Having set forth the basic concepts of the invention, description will now be made of the construction and operation of the photolithographic master with reference being made to the drawing.

The master makes use of a flexible base sheet 10 having a water insoluble, water receptive, hydrophilic, ink repellent, lithographic surface 12 which is overcoated to deposit the combination of a silver halide nucleating agent, sometimes referred to as a fogging agent, and one or more metal salts which operate to enhance the formation of the silver image, its adhesion to the lithographic surface of the master and its ink receptivity thereby to provide a more desirable balance between the hydrophilic character of the nonimaged portions and the oleophilic character of the imaged portions whereby aqueous repellent will wet out the nonimaged portions while the oleophilic ink will preferentially wet out the imaged portions to enable the production of copy by offset.

For this purpose, use can be made of a base sheet formed of a foil of an amphoteric metal such as aluminum, copper or zinc, in which the surface has been treated to render the surface hydrophilic. In the use of aluminum as the base sheet 10, the surface can be rendered hydrophilic by brushing, by anodizing, by an acid etch and preferably by silicating, as described in the Jewett et al. Pat. No. 2,714,066. In the preferred practice of this invention, use is made of a coated paper master in which the base sheet 10 is a resinous treated, high wet strength paper which is provided with a water insoluble, water receptive, hydrophilic, lithographic coating which may be formulated of a binder selected of a hydrophilic colloid, such as casein (U.S. Pat. No. 2,534,650); carboxymethylcellulose (U.S. Pat. No. 2,542,784); alginate (U.S. Pat. No. 2,806,424); zinc polyacrylate (U.S. Pat. No. 2,760,- 431); polyvinyl alcohol; starch and the like, with or without a suitable filler such as zinc oxide, clay, satin white, and the like.

The base sheet is formed with openings 14 at the leading edge for use in mounting the imaged master onto the plate cylinder of a lithographic press but it will be apparent that other means can be employed for engagement of the leading edge of the imaged master for mounting onto the plate cylinder.

As the nucleating agent which is incorporated into the lithographic surface or otherwise incorporated into the treating compositions applied to the surface, best use is made of a stannous halide such as stannous chloride, stannous bromide, stannous hydride and the like, but other silver halide nucleating agents for the conversion of the dissolved silver halide into silver, in the absence of light, can be employed, such as colloidal silver, cadmium sulfide and the like nucleating or fogging agents described in US. Pat. No. 2,352,014.

As the water soluble salts of zirconium, thorium and/ or titanium employed in the treatment of the lithographic surface, use can be made of acetate, propionate, fluoride, bromide, chloride, methylate and nitrate of the respective metals.

It is important to control the amount and ratio of materials applied to the lithographic surface. For example, in the preferred combination of stannous halide and zirconium salt in the treating composition applied to the lithographic surface, it is desirable to maintain the ratio of salts within the range of one part by weight of the stannous salt to 1 to 8 parts by weight of the zirconium salt with an optimum ratio of about 1 to 2.5. When the described combination is employed, it is desirable to deposit the mixture of salts to provide a coating 16 having a coating Weight within the range of 0.1 to 4 grams per square meter and preferably 0.5 to 3 grams per square meter.

As previously pointed out, the preferred practice in the manufacture of a photolithographic master for imaging by diffusion transfer also includes a water soluble cadmium salt. As the cadmium salt, use can be made of an organo cadmium salt represented by cadmium acetate, or an inorganic salt such as cadmium chloride, cadmium bromide, cadmium nitrate or other cadmium halide, and the like. The cadmium salt can be replaced by an antioxidant. When use is made of an antioxidant, it is preferred to make use of such antioxidant in combination with the cadmium salt. Representative of the antioxidants which may be employed are:

ascorbic acid pyrogallic acid catechin hydroquinone di-n-butyl ether hydroquinone monomethyl ether hydroquinone monobenzyl ether hydroquinone diethyl ether hydroquinone dimethyl ether quinone oxyquinoline sulfate S-hydroxyquinoline gallic acid propyl gallate phenidone amidol p-benzoquinone hydroquinone mono-t-butyl hydroquinone 2,5-ditertiary butyl hydroquinone The materials are formulated into a coating composition in the ratio of one part by weight stannous salt per 1 to 8 parts by weight zirconium salt and 0.01 to 0.5 parts by weight cadmium salt, and preferably in an amount within the range of one part by weight stannous salt to 1.7 to 3.5 parts by weight of the zirconium salt and 0.02 to 0.2 part by weight of the cadmium salt. The materials can be formulated into a single coating composition in an amount to provide a solids content of 1 to percent by weight and preferably 2 to 8 percent by weight, and the composition is applied in a coating weight within the range of 0.1 to 4 grams per square meter and preferably within the range of 0.5 to 3 grams per square meter Instead of applying the materials from a single coating composition, the three components can be applied in corresponding amounts in separate coatings to provide one coating containing the cadmium salt, with or without an antioxidant, and another coating containing the zirconium thorium or titanium salt, and a third coating containing the fogging or nucleating agent, or the materials can be formulated into two compositions in various combination.

Application onto the lithographic surface can be made by conventional coating techniques such as spray coating, roller coating, rod coating, flow coating and the like, followed by air drying or drying at elevated temperature such as up to 250 C.

The following are examples of compositions which may be applied as coatings onto the lithographic surface to effect the foregoing treatments:

EXAMPLE 1 Parts by weight Zirconium acetate solution (13% as ZrO 20 Distilled water Stannous chloride 1 Cadmium acetate 0.2

EXAMPLE 2 Zirconium acetate solution (13% as ZrO 2O Distilled water 80 Stannous chloride 2 Cadmium acetate 0.2 Hydroquinone monomethyl ether .20

EXAMPLE 3 Zirconium chloride (13% solution) 20 Distilled water 80 Stannous acetate 2 Cadmium acetate 0.2 Ascorbic acid 0.2

EXAMPLE 4 Zirconium acetate solution (13% as ZrO 20 Water 80 Stannous chloride 2 Hydroquinone monomethyl ether 0.2

EXAMPLE 5 Thorium chloride or titanium chloride (10% solution) 20 Distilled water 80 Stannous chloride 2 Cadmium acetate 0.2 Antioxidant 0.2

EXAMPLE 6 Part A:

Zirconium acetate solution (13% as ZrO 20 Distilled water 80 Stannous chloride 2 Part B:

Cadmium acetate 0.1 Pyrogallic acid 0.2 Distilled water 80 In the preparation of a coated paper lithographic plate, representative of the preferred practice of this invention, use is made of a coated paper direct image plate formed of a high wet strength paper base sheet 10 having a lithographic coating 12 of the type previously described. The lithographic surface of the coated paper base sheet is overcoated with a composition of one of the Examples 1 to 5, applied to provide an overall coating 16 having a coating weight of 0.5 to 3 grams per square meter. The applied coating is dried at elevated temperature within the range of -250" F.

In the use of a plural coating process of Example 6, Part A is applied first onto the lithographic surface. After drying, Part B is applied and dried to provide the plural coating.

Additional improvements can be achieved in the hydrophobic character of the image that is formed on the lithographic surface when the treatment applied to the lithographic surface is formulated of a composition which also contains a sensitizing dyestuff which enhances the formation of a very dense image made up of molecules which are highly hydrophobic in nature from the materials transferred by diffusion from the unexposed porexhibited with dyestuffs included within the group of tions of the silver halide stratum. This phenomenon is exhibited with dyestuffs included within the group of phthalein dyes, and other dyestuffs such as erythrosine, Eosin OI, Eosin Y, Rose Bengal, Rhodamine dyes and the like.

The desired novel effect is secured when the dyestuff is present in the treatment composition in an amount, based upon the coating solids, within the range of 0.001 to 1.0 percent by weight and preferably 0.05 to 0.1 percent by weight, as represented by the following treating compositions:

EXAMPLE 7 20 ml. solution of zirconium acetate (13 as ZrO 80 ml. distilled water 2 g. stannous chloride 0.02 g. cadmium nitrate .2 g. hydroquinone monomethyl ether .5 ml. 1% solution of Rhodamine B EXAMPLE 8 40 ml. solution of zirconium acetate (13 as ZrO 4 g. stannous chloride 160 g. distilled water .40 g. cadmium nitrate .4 g. hydroquinone monomethyl ether .20 g. Eosin O] .05 g. sodium sulfide .002 g. silver nitrate EXAMPLE 9 20 ml. solution of zirconium acetate (13 as ZrO 3 g. stannous chloride 80 g. distilled water .20 g. Eosin OJ.

In accordance with the practice of this invention, the treated surface is overcoated with a negative emulsion coating, as represented by the following example:

EXAMPLE 185 g. silver chloride emulsion (.05 mole) 50 cc. gelatin (4% aqueous solution) cc. distilled water 10 cc. 7.5% aqueous saponin solution .77 cc. formaldehyde solution The negative emulsion coating is applied, as by a rod coater or by other convention coating system, onto the treated surface of the ligthographic master. Application is made in a coating weight which is preferably maintained as low as possible such as within the range of 0.5 to ;5 pounds per 3,000 square feet of surface area, followed by air drying or preferably by drying in a warm air circulating oven having a temperature within the range of 100250 F. Thus the negative emulsion coating 20 is incorporated as an integral part of the photolithographic master to provide a single sheet master which can be used in the preparation of an imaged master by DTR techniques. In use, the coated plate is exposed to a film positive using a conventional photoflood lamp or exposure can be made by other photographic technique, by camera with prism reverser exposure and the like from an original 22.

The exposed plate is developed by wetting with an aqueous alkaline solution containing a silver halide developer and a silver halide solvent, as represented by the following example:

6 EXAMPLE 11 G. Water 815 Phenidone 2.5 Sodium sulfide (anhydrous) 114 Hydroquinone 24 Sodium hydroxide 24 Sodium thiosulfate (anhydrous) 9.8 Potassium bromide 1.6

The liquid developer is applied to wet out the surface of the exposed plate whereby the silver halide in the exposed areas is converted to an insoluble state while the silver halide in the unexposed areas is dissolved and diffused as the salt or as the corresponding silver halide complex to the adjacent underlying treated surface of the lithographic plate where the nucleating agents and salts operate to reduce the diffused soluble silver halide or complex to an ink receptive imaging material which becomes strongly adhered to the lithographic surface. Thus the surface is defined by first imaged areas which are ink recep tive and water repellant and second nonimaged areas which remain water receptive, hydrophilic and lithographic.

The exposed silver halide stratum 20 is swabbed with water or other aqueous medium or by the aqueous conditioner or repellent to remove the silver halide stratum and expose the underlying lithographic surface with the ink receptive silver image 24 anchored onto the surface thereof. Thereafter the imaged plate can be wet with conditioner and with repellent before or after mounting on the lithographic press for the production of multiple copies by conventional lithographic duplicating technique. This includes the step of first wetting the surface of the imaged master with an equeous repellent to wet out the hydrophilic, nonimaged portions 26 of the plate and then with oleaginous ink to wet out the imaged portions 24 after which the inked plate can be brought into contact with the rubber blanket on an offset cylinder for offset duplication or pressed directly onto copy sheets for direct copy reproduction.

In the formulation of the silver halide negative stratum, use can be made of such silver halides as silver chloride, silver bromide, silver hydride and the like.

It will be apparent that I have provided a unique and novel single sheet master which is capable of use in the preparation of an imaged master without the need to employ separate negatives. Thus a single sheet master is provided which is simple and inexpensive in construction and in operation for use in lithographic duplication of copies.

It will be understood that changes may be made in the details of construction, arrangement and operation, without departing from the spirit of the invention, especially as defined in the following claims.

I claim:

1. An offset duplicating master for imaging to provide an ink receptive oleophilic image by diffusion transfer from an exposed silver halide stratum comprising a base sheet having a Water insoluble, water receptive, hydrophilic lithographic surface, said master having on said lithographic surface the combination of a nucleating agent for silver halide, a water soluble salt of a metal selected from the group consisting of zirconium, thorium and titanium as a component separate and apart from the nucleating agent, and a Water soluble salt of cadmium as a component separate and apart from the nucleating agent and in which the materials are present in the ratio of one part by Weight nucleating agent to 1-8 parts by weight of the metal salt to 0.01 to 0.5 part by weight of cadmium salt, and a continuous top coating on the lithographic surface of a silver halide negative stratum.

2. An offset master as claimed in claim 1 in which the silver halide nucleating agent comprises a stannous halide.

3. An offset master as claimed in claim 2 in which the stannous halide metal salt and cadmium salt are present in the same coating.

4. An offset masteras claimed in claim 2 in which the stannous halide metal salt and cadmium salt are present in separate coatings.

5. An offset duplicating master for imaging to provide an ink receptive oleophilic image by diffusion transfer from an exposed silver halide stratum comprising a base sheet having a water insoluble, water receptive, hydrophilic lithographic surface, said master having on said lithographic surface the combination of a nucleating agent for silver halide, a water soluble salt of a metal selected from the group consisting of zirconium, thorium and titanium as a component separate and apart from the nucleating agent and a dyestuff which densifies and renders more hydrophobic and ink receptive the silver image that is formed by reduction of silver halide on the lithographic surface of the master and in which the materials are present in the ratio of one part by Weight of the nucleating agent to 1-8 parts by weight of the metal salt to 0.001 ml percent by Weight of the dyestuff, and a continuous top coating on the lithographic surface of a silver halide negative stratum.

6. An offset master as claimed in claim 5 in which the dyestuff is selected from the group consisting of a phthalein dye; erythrosine, Eosin OJ, Eosin Y, Rose Bengal and Rhodamine dye.

7. An offset master for imaging to provide an ink receptive, olephilic image by difiusion transfer from an exposed silver halide negative comprising a base sheet having a water insoluble, water receptive, hydrophilic lithographic surface, said master having on said lithographic surface the combination of a nucleating agent for silver halide, a Water soluble salt of a metal selected from the group consisting of zirconium, thorium and titanium as a component separate and apart from the nucleating agent, a Water soluble salt of cadmium as a component separate and apart from the nucleating agent and a dyestuff which densifies and renders more hydrophobic and ink receptive the silver image that is formed by reduction of silver halide on the lithographic surface of the master and in which the materials are present in the amount of one part by Weight of the nucleating agent to 1-8 parts by weight of the metal salt to 0.01 to 0.5 part by Weight of cadmium salt and in which the dyestufi is present in an amount within the range of 0.001 to 1 percent by weight, and a continuous top coating on the lithographic surface of a silver halide negative stratum.

References Cited UNITED STATES PATENTS 2,352,014 6/1944 Rott 96-29 2,814,988 12/1957 Bradstreet et al 101-466 3,169,065 2/1965 Sorkin et al. 101456 3,220,837 11/1965 Pond et al 96-29 3,309,990 3/1967 Kliipfel et a1 101-456 3,311,473 3/1967 Foster et al. 9629 FOREIGN PATENTS 202,937 12/1954 Australia 9629 830,623 3/1960 Great Britain 101149.2 856,770 12/1960 Great Britain 101--149.2

GEORGE F. LESMES, Primary Examiner J. P. BRAMMER, Examiner U.S. Cl. X.R.

l0l45l, 453, 467; 96-29, 33

UNITED STATES PATENT OFFICE CERTIFICATE-*0 CORRECTION Patent No. 3,552,970 Dated January 5, 1971 Mary K. Ormsbee It is certified that errors appear in the above corrected as shown below:

Column S, cancel line 7;

Column 5, line 34, change ".20 g. Eosin OJ" to .01 g. Eosin OJ Signed and sealed this 25th day of May 1971.

(SEAL) Attest:

EDL'JARD NJ LETCHEB, J'R. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

